Metals in Dentistry Flashcards
Define elastic modulus.
A measure of a material’s ability to resist elastic deformation. Higher elastic module means more stiff.
Define yield strength
The measure of a material’s ability to resist permanent deformation.
Define flexural strength.
A measure of a material’s ability to resist fracture when bending force is applied.
Define compressive strength.
The measure of a material’s ability to resist being crushed or broken with application of a pushing force.
Define Tensile strength.
The measure of a material’s ability to resist being broken with pulling force.
Define creep.
A measure of the amount of plastic deformation of a material subjected to a compressive force over a given period of time.
Define elongation percent.
The measurement of a material’s ability to be stretched up to its breaking point.
Define Ductility.
A solid materials ability to be plastically deformed under tensile forces without fracture. Stretched into a wire.
Define malleability.
a solid material’s ability to form a thin sheet by hammering or rolling.
Define hardness.
The ability of a solid material to resist plastic deformation.
Define fracture toughness.
Material’s ability to resit fracture in presence of existing crack.
What is dimensional change?
The volumetric change that can occur when the components of a material react to form a product.
Define trituration.
To crush, grind, or pound into small particles.
What is the difference between an amalgam alloy and dental amalgam?
An amalgam alloy is a combination of solid metals. A dental amalgam is an amalgam alloy mixed with Hg.
What does the term eutectic refer to?
When a mixture of substances melt and solidify at a single temperature that is lower than the melting points of the individual parts.
What is the composition of Ag and Cu at the eutectic point?
72% Ag and 28% Cu.
What is the composition of Cu in admixed regular, admixed unicompositional and unicompositional?
Admixed regular the lathe portion has low Cu and the spherical has high Cu. Admixed unicompositional the lathe and spherical has the same amount of CU and the unicompositional is only spherical.
What does Cu do to an alloy?
Increases strength and hardness while decreasing corrosion.
What does Zn do to an alloy? Why is it bad?
Prevents oxidation during manufacturing. Is bad because when there is moisture contamination the zinc will delay expansion.
What does adding the Ag-Cu eutectic to the alloy do?
The Gamma 2 phase is replaced by the eta prime making a harder and more corrosion resistant amalgam.
What are some of the physical differences between admixed alloys and spherical alloys?
Admixed are more condensable and show less post op sensitivity. The spherical give better early strength, smoother surface, require less Hg and more retentive.
What are the setting times for amalgams?
Most will have 60% setting within 1 hour and 100% strength by hour 24.
What are some of the mechanical properties of dental amalgam?
Compressive strength, tensile strength, elastic modulus, creep.
What are some of the physical properties of dental amalgam?
dimensional change, dimensional stability, corrosion resistance, tarnish resistance.
What is the bonding sometimes used in amalgam fillings?
4-META